When the kidney shows partial or overall dysfunction, waste matter that would otherwise be discharged as urine from the body is accumulated in blood, and moreover electrolyte imbalance in the body occurs. As a method for correcting such kidney failure, extracorporeal circulation using a hemodialysis apparatus has been widely performed. Extracorporeal circulation using a hemodialysis apparatus is a method that removes waste matter contained in blood from the body using the principle of diffusion or filtering, and also achieves electrolyte balance.
Typically, a hemodialysis apparatus is configured to outwardly discharge impurities contained in blood using a hemodialysis filter that is equipped with a dialysis membrane within a single housing to enable mass transfer through the dialysis membrane between blood and dialysis fluid. There are two kinds of hemodialysis filters including a hollow fiber membrane type hemodialysis filter and a flat sheet membrane type hemodialysis filter based on the kind of the dialysis membrane.
Among these, the hollow fiber membrane type hemodialysis filter, which is formed by loading a bundle of hollow fiber membranes into a cylindrical container, attaching resin layers to both ends of the bundle, and forming ports through the resin layers, is preferred. This is because the hollow fiber membrane type hemodialysis filter has a large contact area with blood or dialysis fluid despite a small capacity thereof, thus providing superior mass transfer efficiency.
A conventional hemodialysis apparatus includes a hemodialysis filter, a dialysis fluid supply tank for supplying clean dialysis fluid to the hemodialysis filter, a dialysis fluid recovery tank for storing dialysis fluid having passed through the hemodialysis filter, a blood pump for supplying blood to the hemodialysis filter, and a dialysis fluid pump for supplying the dialysis fluid stored in the dialysis fluid supply tank to the hemodialysis filter. The hemodialysis filter is provided with a blood inlet for inflow of blood, a blood outlet for outflow of blood, a dialysis fluid inlet for inflow of dialysis fluid, and a dialysis fluid outlet for outflow of dialysis fluid. Blood and dialysis fluid move in opposite directions within the hemodialysis filter.
Since the blood pump is located toward the blood inlet and the dialysis fluid pump is located toward the dialysis fluid inlet, blood is reduced in pressure with decreasing distance toward the blood outlet, and dialysis fluid is reduced in pressure with decreasing distance toward the dialysis fluid outlet. Diffusion of moisture, electrolyte and waste matter, for example, from blood to dialysis fluid occurs in a region where the pressure of blood is greater than the pressure of dialysis fluid, and dialysis fluid is transferred to blood in a region where the pressure of dialysis fluid is greater than the pressure of blood.